A method for seamless migration of session authentication to a different stateful diameter authenticating peer

ABSTRACT

A method and system that migrates a subscriber session from a first authentication, authorization, and accounting (AAA) authentication server to a second AAA authentication server, where the first AAA authentication server is stateful. The method includes receiving an authenticate session request from a client application, sending (505) the authenticate session request to the first AAA authentication server, detecting (511) connectivity failure with the first AAA authentication server, and sending (513) a reauthentication required message to the client application.

TECHNICAL FIELD

Embodiments of the invention relate to the field of session migration;and more specifically, to the handling of a stateful session migrationbetween authentication peers.

BACKGROUND

Internet service providers (ISP), cellular network providers and similarnetworking infrastructures are designed to enable a large number of enduser devices to have connectivity with services via these networks aswell as access to services via the broader Internet. These networks aregenerally administered by the network provider and the characteristicsof the access (e.g., bandwidth allotment and data allowances) are basedon service contracts between end users and the network providers.

These networks utilize metrics and traffic engineering protocols tomonitor the usage of the network resources by end users and to managethis usage. Often the end user devices connect through local radioaccess networks (e.g., with cellular networks) or via customer premiseequipment (e.g., broadband modems) that are the initial connectingpoints to these provider networks. These components provide accesspoints to the networks and may be connected with various edge devicessuch as border gateways that manage access to the broader providernetwork. These border gateways (e.g., broadband network gateway (BNG))or edge routers may service the end user devices and work in connectionwith authentication, authorization, and accounting (AAA) services in theprovider network to keep metrics and accounting relative to each enduser.

For example, the AAA services in the provider network can authenticateor authorize initial end user access to the provider networks. The AAAservices can also configure the characteristics of the end user accessat the BNG or similar network devices in the provider network. The AAAservices can use various protocols for the network devices in theprovider network to interact with them. One AAA protocol that iscommonly utilizes is the remote authentication dial-in user service(RADIUS). A closely related AAA protocol called Diameter was initiallydesigned to replace RADIUS, but RADIUS has continued to be utilized inmany types of networks with Diameter being utilized in others.

SUMMARY

In one embodiment, a method and system migrates a subscriber sessionfrom a first authentication, authorization, and accounting (AAA)authentication server to a second AAA authentication server, where thefirst AAA authentication server is stateful. The method includesreceiving an authenticate session request from a client application,sending (505) the authenticate session request to the first AAAauthentication server, detecting (511) connectivity failure with thefirst AAA authentication server, and sending (513) a reauthenticationrequired message to the client application.

In a further embodiment, a network device is configured to execute aplurality of virtual machines. The virtual machines are configured tosupport network function virtualization (NFV). The plurality of virtualmachines support the method for migrating a subscriber session from thefirst AAA authentication server to the second AAA authentication server,where the first AAA authentication server is stateful. The networkdevice includes a non-transitory computer readable medium having storedtherein a AAA client, and a processor coupled to the non-transitorycomputer readable medium configured to execute a virtual machine fromthe plurality of virtual machine. The virtual machine executes the AAAclient. The AAA client is configured to receive an authenticate sessionrequest from a client application, to send the authenticate sessionrequest to the first AAA authentication server, to detect connectivityfailure with the first AAA authentication server, and to send areauthentication required message to the client application.

In another embodiment, a computing device is configured to execute themethod for migrating a subscriber session from the first AAAauthentication server to the second AAA authentication server, where thefirst AAA authentication server is stateful. The computing deviceincludes a non-transitory computer readable medium having stored thereinthe AAA client, and a processor coupled to the non-transitory computerreadable medium configured to execute the AAA client. The AAA client isconfigured to receive an authenticate session request from a clientapplication, to send the authenticate session request to the first AAAauthentication server, to detect connectivity failure with the first AAAauthentication server, and to send a reauthentication required messageto the client application.

In one embodiment, a control plane device is in a network including aplurality of data plane devices. The control plane device is incommunication with the plurality of data plane devices and is configuredto implement the method for migrating a subscriber session from a firstAAA authentication server to a second AAA authentication server, wherethe first AAA authentication server is stateful. The control planedevice includes a non-transitory computer readable medium having storedtherein the AAA client, and a processor coupled to the non-transitorycomputer readable medium configured to execute the AAA client. The AAAclient is configured to receive an authenticate session request from aclient application, to send the authenticate session request to thefirst AAA authentication server, to detect connectivity failure with thefirst AAA authentication server, and to send a reauthentication requiredmessage to the client application.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may best be understood by referring to the followingdescription and accompanying drawings that are used to illustrateembodiments of the invention. In the drawings:

FIG. 1 is a diagram of one embodiment of an example network including anauthentication, authorization, and accounting (AAA) service.

FIG. 2 is a diagram of one embodiment of a process for authenticationbetween a client application and an authentication peer.

FIG. 3 is a diagram of one embodiment of a process for an authenticationpeer to request a reauthentication between a client application and theauthentication peer.

FIG. 4 is a diagram of one embodiment of a process for handling atransparent migration to a new AAA server, where the existing AAA serverfailure is detected by the

AAA client.

FIG. 5 is a diagram of one embodiment of the migration process at thenetwork device executing the AAA client.

FIG. 6A illustrates connectivity between network devices (NDs) within anexemplary network, as well as three exemplary implementations of theNDs, according to some embodiments of the invention.

FIG. 6B illustrates an exemplary way to implement a special-purposenetwork device according to some embodiments of the invention.

FIG. 6C illustrates various exemplary ways in which virtual networkelements (VNEs) may be coupled according to some embodiments of theinvention.

FIG. 6D illustrates a network with a single network element (NE) on eachof the NDs, and within this straight forward approach contrasts atraditional distributed approach (commonly used by traditional routers)with a centralized approach for maintaining reachability and forwardinginformation (also called network control), according to some embodimentsof the invention.

FIG. 6E illustrates the simple case of where each of the NDs implementsa single NE, but a centralized control plane has abstracted multiple ofthe NEs in different NDs into (to represent) a single NE in one of thevirtual network(s), according to some embodiments of the invention.

FIG. 6F illustrates a case where multiple VNEs are implemented ondifferent NDs and are coupled to each other, and where a centralizedcontrol plane has abstracted these multiple VNEs such that they appearas a single VNE within one of the virtual networks, according to someembodiments of the invention.

FIG. 7 illustrates a general-purpose control plane device withcentralized control plane (CCP) software 750), according to someembodiments of the invention.

DETAILED DESCRIPTION

The following description describes methods and apparatus for enabling atransparent migration of a stateful authentication session between oneauthentication server and another authentication service. Theembodiments identify a failure of a first authentication server and senda reauthentication request message to a client application. The clientapplication is thereby caused to request a re-authentication of thesession by sending an authentication session request. The newauthentication session request will be sent to an available secondauthentication server to establish a new authentication session with thesecond authentication server in a manner that is transparent to theclient application and second authentication server. This processminimizes the time for migrating an authentication session withoutrequiring modification of or visibility at the client application of thefailure of the first authentication server.

In the following description, numerous specific details such as logicimplementations, opcodes, means to specify operands, resourcepartitioning/sharing/duplication implementations, types andinterrelationships of system components, and logicpartitioning/integration choices are set forth in order to provide amore thorough understanding of the present invention. It will beappreciated, however, by one skilled in the art that the invention maybe practiced without such specific details. In other instances, controlstructures, gate level circuits and full software instruction sequenceshave not been shown in detail in order not to obscure the invention.Those of ordinary skill in the art, with the included descriptions, willbe able to implement appropriate functionality without undueexperimentation.

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

Bracketed text and blocks with dashed borders (e.g., large dashes, smalldashes, dot-dash, and dots) may be used herein to illustrate optionaloperations that add additional features to embodiments of the invention.However, such notation should not be taken to mean that these are theonly options or optional operations, and/or that blocks with solidborders are not optional in certain embodiments of the invention.

In the following description and claims, the terms “coupled” and“connected,” along with their derivatives, may be used. It should beunderstood that these terms are not intended as synonyms for each other.“Coupled” is used to indicate that two or more elements, which may ormay not be in direct physical or electrical contact with each other,co-operate or interact with each other. “Connected” is used to indicatethe establishment of communication between two or more elements that arecoupled with each other.

An electronic device stores and transmits (internally and/or with otherelectronic devices over a network) code (which is composed of softwareinstructions and which is sometimes referred to as computer program codeor a computer program) and/or data using machine-readable media (alsocalled computer-readable media), such as machine-readable storage media(e.g., magnetic disks, optical disks, solid state drives, read onlymemory (ROM), flash memory devices, phase change memory) andmachine-readable transmission media (also called a carrier) (e.g.,electrical, optical, radio, acoustical or other form of propagatedsignals—such as carrier waves, infrared signals). Thus, an electronicdevice (e.g., a computer) includes hardware and software, such as a setof one or more processors (e.g., wherein a processor is amicroprocessor, controller, microcontroller, central processing unit,digital signal processor, application specific integrated circuit, fieldprogrammable gate array, other electronic circuitry, a combination ofone or more of the preceding) coupled to one or more machine-readablestorage media to store code for execution on the set of processorsand/or to store data. For instance, an electronic device may includenon-volatile memory containing the code since the non-volatile memorycan persist code/data even when the electronic device is turned off(when power is removed), and while the electronic device is turned onthat part of the code that is to be executed by the processor(s) of thatelectronic device is typically copied from the slower non-volatilememory into volatile memory (e.g., dynamic random access memory (DRAM),static random access memory (SRAM)) of that electronic device. Typicalelectronic devices also include a set or one or more physical networkinterface(s) (NI(s)) to establish network connections (to transmitand/or receive code and/or data using propagating signals) with otherelectronic devices. For example, the set of physical NIs (or the set ofphysical NI(s) in combination with the set of processors executing code)may perform any formatting, coding, or translating to allow theelectronic device to send and receive data whether over a wired and/or awireless connection. In some embodiments, a physical NI may compriseradio circuitry capable of receiving data from other electronic devicesover a wireless connection and/or sending data out to other devices viaa wireless connection. This radio circuitry may include transmitter(s),receiver(s), and/or transceiver(s) suitable for radiofrequencycommunication. The radio circuitry may convert digital data into a radiosignal having the appropriate parameters (e.g., frequency, timing,channel, bandwidth, etc.). The radio signal may then be transmitted viaantennas to the appropriate recipient(s). In some embodiments, the setof physical NI(s) may comprise network interface controller(s) (NICs),also known as a network interface card, network adapter, or local areanetwork (LAN) adapter. The NIC(s) may facilitate in connecting theelectronic device to other electronic devices allowing them tocommunicate via wire through plugging in a cable to a physical portconnected to a NIC. One or more parts of an embodiment of the inventionmay be implemented using different combinations of software, firmware,and/or hardware.

A network device (ND) is an electronic device that communicativelyinterconnects other electronic devices on the network (e.g., othernetwork devices, end-user devices). Some network devices are “multipleservices network devices” that provide support for multiple networkingfunctions (e.g., routing, bridging, switching, Layer 2 aggregation,session border control, Quality of Service, and/or subscribermanagement), and/or provide support for multiple application services(e.g., data, voice, and video).

The embodiments are compatible with various authentication andaccounting protocols. One skilled in the art would appreciate that theprinciples, processes, and structures described herein are applicable toother authentication, authorization, and accounting (AAA) protocols,however, the examples herein are primarily drawn to the Diameterprotocol for sake of conciseness and clarity.

Diameter

The Diameter protocol is an AAA protocol which is widely used in thecellular or ‘mobile’ networks. Increasingly, with fixed-mobileconvergence (FMC) of increased interest, i.e., the use of the sametechnologies in traditional ‘fixed’ networks and current ‘mobile’networks, broadband remote access (BRAS) gateways and broadband networkgateways (BNGs) are also starting to feature Diameter as the primary AAAprotocol, often replacing RADIUS and similar technologies.

The Diameter protocol consists of a base protocol (defined in RFC-6733)and Diameter applications which can be defined by various standardbodies. The Diameter base protocol defines various Diameter nodes,including Diameter Clients, Servers, and Agents. Diameter Clients talksto Diameter Servers, either directly or via Diameter Agents. As usedherein, a ‘Diameter Peer,’ is discussed, which could be either aDiameter Server or an Diameter Agent. More generally, each of thesecomponents could be referred to as AAA clients, servers, agents, andpeers.

Diameter Clients are typically the AAA enforcing nodes, such as the BNGnode. A Diameter Client can be characterized as including at least twological components, namely, a Client Application of Diameter (herein aDiameter Client Application, client application or more generally an AAAclient application), which is a client application of the Diameterprotocol and a Diameter Client Protocol Stack (herein a Diameterprotocol stack or more generally an AAA protocol stack), which providesDiameter protocol service to one or more of the Diameter ClientApplications. The Diameter Clients need connectivity to a Diameter Peersuch as a Diameter Server in order to perform all of the normal AAAactions. The Diameter Servers could be stateful, i.e., the DiameterServers have a particular operating ‘state’ that defines the currentoperation of the Diameter Server. The current state can be aconfiguration of the Diameter Server and its resources and may bemanaged by an internal state machine. For stateful authentication, forany AAA session, the Diameter server and its authentication componentsneed to receive “AA-Request/AA-Answer (AAR/AAA)” messages at thebeginning of the session and “Session Termination Request/SessionTermination Answer (STR/STA)” messages at the end of the session. TheDiameter protocol defines both stateless and stateful mode for Diameterauthentication servers

For redundancy and load-balancing reasons, multiple Diameter Peers(i.e., multiple Diameter Servers) are configured. When subscribersessions (communication sessions between the Diameter client and asubscriber related device) are being handled, the BNG node (executingthe Diameter Client) chooses a specific Diameter Peer (Diameter Server)at subscriber session establishment time, based on a variety ofload-balancing algorithm considerations. The Diameter Peer remainsassociated with the subscriber session for the lifetime of the session.

AAA in Network Architecture

FIG. 1 is a diagram of one embodiment of an example network where an AAAprotocol may be utilized. In this simplified example, a set of clientdevices 101 that connect to a network provided by an Internet ServiceProvider (ISP) or mobile service provider. The example illustrates afixed network, but the principles and techniques are equally applicableto a mobile network. In the example, the client devices 101 connect toresidential gateways (RGWs) or similar network devices that are the edgeof the ISP or mobile network. The home or local networks of the usersmay include additional devices such as access points and home routers.The RGWs provide connectivity to an access network 105 that enable anumber of various subscribers (i.e., the owners of the client devices101) to connect to the Internet and services provided by the ISP ormobile network. The RGWs enable connection to BNGs or BRAS via theaccess network.

The BNG (or BRAS) 107 provides various services for managing subscriberservices including enforcing AAA policies. The BNG may handle many typesof subscribers. The subscriber type is based on how a subscriber sessionis setup with the BNG. Dynamic session establishment is done usingprotocols such as point to point over Ethernet (PPPoE/PPP) or Layer 2tunneling protocol (L2TP/PPP) and using Dynamic Host ConfigurationProtocol (DHCP) protocols. There are also modes to setup a subscribersession based on Internet Protocol (IP)-packet flow from the subscriber.A dynamic session is established in response to the subscriberconnecting to the BNG. A static session establishment is done viaconfiguration. Such subscriber sessions are long lived sessions, i.e., astatic session is established once configured by an administrator andmust remain functioning until torn down via configuration by anadministrator.

The BNG 107 can implement the AAA functions for enforcement of policieson subscriber sessions via an AAA client (e.g., a Diameter Client). TheAAA client communicates with an AAA server 109 (e.g., a DiameterServer). The AAA server manages the policies and performs accountingfunctions, authorization functions and authentication functions. The AAAserver then directs or configures the AAA client to implement the AAApolicies as needed. Such AAA policies can manage the subscriber accessto other services and the Internet 111 including refusing connections,managing bandwidth and tracking resource usage according to a subscribercontract.

FIG. 2 is a diagram of one embodiment of a process for authenticationbetween a client application and an authentication peer. In thisexample, a client application can be any application, often implementedat the BNG or similar subscriber gateway nodes, that communicates withan AAA server in this case a stateful AAA server. A client applicationthat needs to use the AAA (e.g., Diameter) protocol will interact withthe following logical components an AAA (e.g., Diameter) stack, whichhandles the AAA protocol aspects of the communication with the AAAserver (e.g., a Diameter Server/Peer) and a AAA (e.g., Diameter) clientapplication, which uses the AAA (e.g., Diameter) stack to exchangeinformation with AAA peers. A single AAA stack instance could provideAAA protocol handling support to multiple AAA client applications. Thediagram of FIG. 1 illustrates a simple session authentication case.

The client application initiates the session with an authenticatesession request message that is sent to AAA (e.g., Diameter) stackoperating in client mode, which can be referred to as the AAA client.The AAA client generates an authentication request that it sends to theAAA server, e.g., a) Authentication Authorization Request (AAR) message.In some embodiments, the AAR can be a Network Access Server Requirements(NASREQ) message. NASREQ is defined in RFC 7155. For redundancy andload-balancing reasons, multiple AAA servers are configured. Theauthentication request includes credentials from the client applicationthat enable the AAA server to authenticate the client application andwhich enable the client application to utilize services of the networkwhere the AAA server serves as a gatekeeper. When a subscriberauthentication session is being handled, the client application, e.g.,at the BNG node, chooses a specific AAA server, (e.g., a Diameter peer)at authentication session establishment time, based on a variety ofpossible load-balancing algorithms. The AAA server (e.g., a Diameterpeer) remains associated with the session for the lifetime of thesession. Diameter protocol (RFC-6733, Sec-8.1) defines both statelessand stateful mode for Diameter authentication/authorization servers.

The AAA server responds to the authentication request with anauthentication answer, e.g., an Authentication Authorization—Answer(AAA) message that indicates authentication success. The AAA message canbe a NASREQ AAA message. The AAA client then sends an authenticationsuccess message to the client application. The authentication sessionthen persists and session activity can remain continuous until theclient application decides to terminate the authenticate session. Theclient application in this case sends a terminate session message to theAAA client. The AAA client relays a session termination request to theAAA server. The AAA server replies with a session termination responsethat indicates an acknowledgement that the authenticate session isterminating at the AAA server. The AAA client relays this message as atermination done message to the client application.

Problems with this system occur where there is an interruption in thecommunication with the AAA peer (e.g., the AAA server). For the Diameterprotocol for example, the Diameter base protocol defines one optionalserver-side state machine that may be utilized by applications thatrequire keeping track of the session state at the AAA server. Suchtracking is incompatible with the ability to handle long durationconnectivity problems.

FIG. 3 is a diagram of one embodiment of a process for an authenticationpeer to request a reauthentication between a client application and theauthentication peer. The AAA server (e.g., a Diameter authenticationserver) can request that a client application reauthenticate a session.This can be done, for example, when some settings for a subscriber arechanged and need to be applied on that subscriber's session. FIG. 3provides an example exchange where reauthentication is requested by theAAA server.

In this example, the client application and AAA server have alreadyestablished an authentication session. The AAA server decides that areauthentication of the session is needed. The AAA server sends areauthentication requests to the AAA client. The AAA client then sends areauthentication required message to the client application. The clientapplication responds with a reauthentication request acknowledgement tothe AAA client. The AAA client sends a reauthentication acknowledgementto the AAA server.

The client application then sends an authenticate session request to theAAA client. The AAA client generates an authentication request, e.g., anAA-R message and sends it to the AAA server. The AAA server sends andauthentication response, e.g., an AA-A message indicating success to theAAA client. The AAA client sends an authentication success message tothe client application and the authentication session isre-authenticated.

Overview of Authentication Session Migration

An example scenario for authentication session migration is where anauthentication session is established with a specific stateful AAAserver (e.g., a Diameter NASREQ peer) for providing authentication andauthorization services to a client application and AAA client. Migrationis utilized in the case where the AAA server has gone down for anyreason. This migration involves a new authentication/authorizationhandshake (AA-Request, AA-Answer) be done with a new stateful AAA server(e.g., a Diameter NASREQ peer) that is still functioning.

Without the embodiments, the migration would require that the clientapplication be made aware of the AAA server failure and that the clientapplication initiate a re-handshake to establish a new session with thenew AAA server. However, if the AAA stack is considered as amicroservice, the requirement being imposed on all client applicationsthat use the microservice to be aware of server transition addscomplexity to client applications and where the client application isnot modified to identify the failure of the AAA server, then nomigration is possible and the session fails.

The embodiments design the AAA stack to avoid client applications havingAAA server availability awareness and explicit AAA server transition.The AAA client could be modified to cache the AA-request and replay itlater in response to a AAA server failure. But this causes significantmemory resource usage at the AAA client (e.g., a Diameter stackmicroservice most store a large number of these responses for replay).This options also includes significant complexity in AAA stack, due to aneed for garbage collection to handle client application interfaceerrors. If this potential implementation or existing implementationsdrop the authentication session due to AAA server failure it would causepoor user experience due to a disruption in service. While disruptionsin service can be feasible for mobile subscribers, it is not feasiblefor BNG subscribers.

For BNG subscriber sessions established via DHCP as the sessionsignaling protocol, there is no way to signal the subscriber to bringdown the session. Enhancements to DHCP such as “DHCP FORCERENEW” are notwidely implemented by many DHCP clients. The only way to deal with thisis to have short lease times provided to subscribers. But that justreduces the disruption time when the session is brought down due toauthentication server connectivity issues. For static subscribersessions, there is no supported teardown of a session for subscribers,since teardown happens via configuration removal. It is possible to doan implicit teardown and bring up of a session immediately, but thatcauses traffic disruption and loss.

The embodiments overcome these issues and provide, in the event ofconnectivity disruption to a AAA authentication server that has beenassigned to a session (chosen at session establishment time frommultiple available AAA servers), to be able to choose another AAAauthentication server and send subsequent packets of the given sessionto the newly selected authentication server.

The embodiments also insulate the client application from the knowledgeof such changes to the assigned AAA server associated with a session. Inthis manner, the embodiments avoid client applications needing to knowabout the AAA server or AAA server connection issues in a transparentway and helps remove complexity from client applications. Clientapplications can thus focus only on information generation andconsumption and leave AAA server resiliency aspects to the AAA stack.

FIG. 4 is a diagram of one embodiment of a process for handling atransparent migration to a new AAA server, where the existing AAA serverfailure is detected by the

AAA client. When a client application seeks to establish a session, itsignals the AAA client (e.g., a Diameter stack) with an authenticatesession request. The AAA client selects a AAA authentication server,from the available set of AAA authentication servers. The AAAauthentication servers may notify connected AAA clients or the AAAclient may poll the AAA authentication servers to determineavailability. The authentication exchange will happen with this selectedAAA authentication server. The AAA client sends the authenticationrequest to the selected AAA server, e.g., a AA-R message is sent. Theselected AAA server responds to the AAA client with an authenticationanswer indicating successful authentication of the client application,e.g., via an AA-A message. In normal course, when the client applicationhas completed a session, the termination request would happen with thissame AAA server.

However, when the selected AAA authentication server fails, e.g., wherea Diameter authentication server fails, the AAA client detects thisfailure and chooses a new server from the remaining set of availableservers. The AAA client also makes note of this transition. To the newAAA server. The AAA client can track available AAA authenticationservers by polling the known AAA authentication servers, by receivingadvertisements of availability from the AAA authentication servers orthrough similar mechanisms and combinations thereof.

Upon detecting a failure with the selected AAA authentication server,the AAA client generates and sends a “fake reauthorization required”message to the client. The reauthorization request message is ‘fake,’ inthe sense that the AAA client generates the reauthorization requiredmessage as though it was generated by or responsive to a request fromthe new AAA server. The client application responds with areauthentication request acknowledgement to this ‘fake’ message, whichis discarded by the AAA stack. In contrast, in normal operation thereauthorization would be generated based on a request form the AAAserver and the acknowledgement would similarly be relayed to the AAAserver as described herein above. However, in this case where the AAAserver has failed, no reauthentication acknowledgment protocol messageis sent out.

After the client application sends the reauthentication requestacknowledgement, the client application sends a new authenticate sessionrequest to the AAA client, which will initiate an authentication requestwith a newly selected available AAA server, e.g., as a AA-R message asrequired by the NASREQ protocol. This authentication request message, isdirected by the AAA stack to the newly selected and available AAAserver. This authentication request message establishes a new sessionbetween the client application and the new AAA server, without eitherbeing aware of the migration. Later, at session termination time, theclient application will perform a termination exchange with this secondAAA server, assuming it continues to function without failure.

FIG. 5 is a diagram of one embodiment of the migration process at thenetwork device executing the AAA client. The AAA client engages in thesession authentication in response to receiving an authenticate sessionrequest from a client application (Block 501). The AAA client thenselects one of the available authentication servers, i.e., an AAAserver, which may be a Diameter server (Block 503). The AAA client maybe able to track available AAA servers via advertisements from the AAAservers or by polling known AAA servers. Each of the AAA servers may bestateful that are available may be stateful. The AAA client sends anauthentication request to the selected AAA authentication server (Block505).

The selected AAA authentication server authenticates the credentials ofthe client application or the underlying subscriber that are included inthe authenticate session request. Any type of credentials or similarinformation may be provided, e.g., as described by the NASREQ protocol,and any algorithm may be utilized to authenticate the credentials at theAAA authentication server.

The AAA client receives an authentication success message from theselected AAA authentication server (Block 507). Alternatively, a failureor error message may be received or occur in which case a session is notestablished between the client application and the AAA authenticationserver. An error may in some embodiments be returned to the clientapplication, whereas in other embodiments no information is returned tothe client application. The AAA client sends an authentication successmessage to the client application in response to the authenticationsuccess message received from the AAA authentication server (Block 509).In some embodiments, the same protocols and message types are utilizedbetween the client application and AAA client as are used between theAAA client and the AAA authentication server, e.g., NASREQ protocol.However, in other embodiments, different message types and protocols areutilized between the client application and the AAA client than are usedbetween the AAA client and the AAA authentication server.

While the selected AAA authentication server continues to function andbe available to the AAA client, the session operates normally. However,the AAA client monitors the AAA authentication server status for failure(Block 513). In the case where a failure is detected, then the AAAclient generates and sends a ‘fake’ reauthentication required message tothe client application, to cause the client application to send a newauthenticate session request that can be sent to a new AAAauthentication server. The AAA client then receives an acknowledgementof the reauthentication required message from the client application(Block 515). The subsequent authenticate request message will be handledas a new authentication session and the set of available AAAauthentication servers will remove the failed AAA authentication server.That is, the process will begin again (Block 501). Thus, but iteratingthrough the process of FIG. 5, a new stateful AAA server can be selectedto replace a failed stateful AAA server in response to the failure.

The embodiments thereby provide advantages over the prior art. Clientapplications need not require any complexity of awareness of AAA serverstatus (e.g., of Diameter peers) used to provide authentication servicesand do not require awareness of the AAA server failures and relatedresiliency handling aspects. The application programming interface (API)between the AAA client (e.g., a Diameter stack) and client applicationis kept only to the messaging protocol required exchanges. Theembodiments also provide simpler implementation in the AAA client tohandle AAA authentication server transition (as compared to alternateimplementation possibilities for providing this migration as discussedabove).

FIG. 6A illustrates connectivity between network devices (NDs) within anexemplary network, as well as three exemplary implementations of theNDs, according to some embodiments of the invention. FIG. 6A shows NDs600A-H, and their connectivity by way of lines between 600A-600B,600B-600C, 600C-600D, 600D-600E, 600E-600F, 600F-600G, and 600A-600G, aswell as between 600H and each of 600A, 600C, 600D, and 600G. These NDsare physical devices, and the connectivity between these NDs can bewireless or wired (often referred to as a link). An additional lineextending from NDs 600A, 600E, and 600F illustrates that these NDs actas ingress and egress points for the network (and thus, these NDs aresometimes referred to as edge NDs; while the other NDs may be calledcore NDs).

Two of the exemplary ND implementations in FIG. 6A are: 1) aspecial-purpose network device 602 that uses custom application—specificintegrated—circuits (ASICs) and a special-purpose operating system (OS);and 2) a general-purpose network device 604 that uses commonoff-the-shelf (COTS) processors and a standard OS.

The special-purpose network device 602 includes networking hardware 610comprising a set of one or more processor(s) 612, forwarding resource(s)614 (which typically include one or more ASICs and/or networkprocessors), and physical network interfaces (NIs) 616 (through whichnetwork connections are made, such as those shown by the connectivitybetween NDs 600A-H), as well as non-transitory machine-readable storagemedia 618 having stored therein networking software 620. Duringoperation, the networking software 620 may be executed by the networkinghardware 610 to instantiate a set of one or more networking softwareinstance(s) 622. Each of the networking software instance(s) 622, andthat part of the networking hardware 610 that executes that networksoftware instance (be it hardware dedicated to that networking softwareinstance and/or time slices of hardware temporally shared by thatnetworking software instance with others of the networking softwareinstance(s) 622), form a separate virtual network element 630A-R. Eachof the virtual network element(s) (VNEs) 630A-R includes a controlcommunication and configuration module 632A-R (sometimes referred to asa local control module or control communication module) and forwardingtable(s) 634A-R, such that a given virtual network element (e.g., 630A)includes the control communication and configuration module (e.g.,632A), a set of one or more forwarding table(s) (e.g., 634A), and thatportion of the networking hardware 610 that executes the virtual networkelement (e.g., 630A).

The special-purpose network device 602 is often physically and/orlogically considered to include: 1) a ND control plane 624 (sometimesreferred to as a control plane) comprising the processor(s) 612 thatexecute the control communication and configuration module(s) 632A-R;and 2) a ND forwarding plane 626 (sometimes referred to as a forwardingplane, a data plane, or a media plane) comprising the forwardingresource(s) 614 that utilize the forwarding table(s) 634A-R and thephysical NIs 616. By way of example, where the ND is a router (or isimplementing routing functionality), the ND control plane 624 (theprocessor(s) 612 executing the control communication and configurationmodule(s) 632A-R) is typically responsible for participating incontrolling how data (e.g., packets) is to be routed (e.g., the next hopfor the data and the outgoing physical NI for that data) and storingthat routing information in the forwarding table(s) 634A-R, and the NDforwarding plane 626 is responsible for receiving that data on thephysical NIs 616 and forwarding that data out the appropriate ones ofthe physical NIs 616 based on the forwarding table(s) 634A-R.

FIG. 6B illustrates an exemplary way to implement the special-purposenetwork device 602 according to some embodiments of the invention. FIG.6B shows a special-purpose network device including cards 638 (typicallyhot pluggable). While in some embodiments the cards 638 are of two types(one or more that operate as the ND forwarding plane 626 (sometimescalled line cards), and one or more that operate to implement the NDcontrol plane 624 (sometimes called control cards)), alternativeembodiments may combine functionality onto a single card and/or includeadditional card types (e.g., one additional type of card is called aservice card, resource card, or multi-application card). A service cardcan provide specialized processing (e.g., Layer 4 to Layer 7 services(e.g., firewall, Internet Protocol Security (IPsec), Secure SocketsLayer (SSL)/Transport Layer Security (TLS), Intrusion Detection System(IDS), peer-to-peer (P2P), Voice over IP (VoIP) Session BorderController, Mobile Wireless Gateways (Gateway General Packet RadioService (GPRS) Support Node (GGSN), Evolved Packet Core (EPC) Gateway)).By way of example, a service card may be used to terminate IPsec tunnelsand execute the attendant authentication and encryption algorithms.These cards are coupled together through one or more interconnectmechanisms illustrated as backplane 636 (e.g., a first full meshcoupling the line cards and a second full mesh coupling all of thecards).

Returning to FIG. 6A, the general-purpose network device 604 includeshardware 640 comprising a set of one or more processor(s) 642 (which areoften COTS processors) and physical NIs 646, as well as non-transitorymachine-readable storage media 648 having stored therein software 650.During operation, the processor(s) 642 execute the software 650 toinstantiate one or more sets of one or more applications 664A-R. Whileone embodiment does not implement virtualization, alternativeembodiments may use different forms of virtualization. For example, inone such alternative embodiment the virtualization layer 654 representsthe kernel of an operating system (or a shim executing on a baseoperating system) that allows for the creation of multiple instances662A-R called software containers that may each be used to execute one(or more) of the sets of applications 664A-R; where the multiplesoftware containers (also called virtualization engines, virtual privateservers, or jails) are user spaces (typically a virtual memory space)that are separate from each other and separate from the kernel space inwhich the operating system is run; and where the set of applicationsrunning in a given user space, unless explicitly allowed, cannot accessthe memory of the other processes. In another such alternativeembodiment the virtualization layer 654 represents a hypervisor(sometimes referred to as a virtual machine monitor (VMM)) or ahypervisor executing on top of a host operating system, and each of thesets of applications 664A-R is run on top of a guest operating systemwithin an instance 662A-R called a virtual machine (which may in somecases be considered a tightly isolated form of software container) thatis run on top of the hypervisor—the guest operating system andapplication may not know they are running on a virtual machine asopposed to running on a “bare metal” host electronic device, or throughpara-virtualization the operating system and/or application may be awareof the presence of virtualization for optimization purposes. In yetother alternative embodiments, one, some or all of the applications areimplemented as unikernel(s), which can be generated by compilingdirectly with an application only a limited set of libraries (e.g., froma library operating system (LibOS) including drivers/libraries of OSservices) that provide the particular OS services needed by theapplication. As a unikernel can be implemented to run directly onhardware 640, directly on a hypervisor (in which case the unikernel issometimes described as running within a LibOS virtual machine), or in asoftware container, embodiments can be implemented fully with unikernelsrunning directly on a hypervisor represented by virtualization layer654, unikernels running within software containers represented byinstances 662A-R, or as a combination of unikernels and theabove-described techniques (e.g., unikernels and virtual machines bothrun directly on a hypervisor, unikernels and sets of applications thatare run in different software containers).

The instantiation of the one or more sets of one or more applications664A-R, as well as virtualization if implemented, are collectivelyreferred to as software instance(s) 652. Each set of applications664A-R, corresponding virtualization construct (e.g., instance 662A-R)if implemented, and that part of the hardware 640 that executes them (beit hardware dedicated to that execution and/or time slices of hardwaretemporally shared), forms a separate virtual network element(s) 660A-R.The Applications 664A-R can include AAA clients as described herein. TheAAA clients may encompass AAA client applications and/or AAA protocolstacks. These embodiments further encompass Diameter implementations.

The virtual network element(s) 660A-R perform similar functionality tothe virtual network element(s) 630A-R—e.g., similar to the controlcommunication and configuration module(s) 632A and forwarding table(s)634A (this virtualization of the hardware 640 is sometimes referred toas network function virtualization (NFV)). Thus, NFV may be used toconsolidate many network equipment types onto industry standardhigh-volume server hardware, physical switches, and physical storage,which could be located in Data centers, NDs, and customer premiseequipment (CPE). While embodiments of the invention are illustrated witheach instance 662A-R corresponding to one VNE 660A-R, alternativeembodiments may implement this correspondence at a finer levelgranularity (e.g., line card virtual machines virtualize line cards,control card virtual machine virtualize control cards, etc.); it shouldbe understood that the techniques described herein with reference to acorrespondence of instances 662A-R to VNEs also apply to embodimentswhere such a finer level of granularity and/or unikernels are used.

In certain embodiments, the virtualization layer 654 includes a virtualswitch that provides similar forwarding services as a physical Ethernetswitch. Specifically, this virtual switch forwards traffic betweeninstances 662A-R and the physical NI(s) 646, as well as optionallybetween the instances 662A-R; in addition, this virtual switch mayenforce network isolation between the VNEs 660A-R that by policy are notpermitted to communicate with each other (e.g., by honoring virtuallocal area networks (VLANs)).

The third exemplary ND implementation in FIG. 6A is a hybrid networkdevice 606, which includes both custom ASICs/special-purpose OS and COTSprocessors/standard OS in a single ND or a single card within an ND. Incertain embodiments of such a hybrid network device, a platform VM(i.e., a VM that that implements the functionality of thespecial-purpose network device 602) could provide forpara-virtualization to the networking hardware present in the hybridnetwork device 606.

Regardless of the above exemplary implementations of an ND, when asingle one of multiple VNEs implemented by an ND is being considered(e.g., only one of the VNEs is part of a given virtual network) or whereonly a single VNE is currently being implemented by an ND, the shortenedterm network element (NE) is sometimes used to refer to that VNE. Alsoin all of the above exemplary implementations, each of the VNEs (e.g.,VNE(s) 630A-R, VNEs 660A-R, and those in the hybrid network device 606)receives data on the physical NIs (e.g., 616, 646) and forwards thatdata out the appropriate ones of the physical NIs (e.g., 616, 646). Forexample, a VNE implementing IP router functionality forwards IP packetson the basis of some of the IP header information in the IP packet;where IP header information includes source IP address, destination IPaddress, source port, destination port (where “source port” and“destination port” refer herein to protocol ports, as opposed tophysical ports of a ND), transport protocol (e.g., user datagramprotocol (UDP), Transmission Control Protocol (TCP), and differentiatedservices code point (DSCP) values.

FIG. 6C illustrates various exemplary ways in which VNEs may be coupledaccording to some embodiments of the invention. FIG. 6C shows VNEs670A.1-670A.P (and optionally VNEs 670A.Q-670A.R) implemented in ND 600Aand VNE 670H.1 in ND 600H. In FIG. 6C, VNEs 670A.1-P are separate fromeach other in the sense that they can receive packets from outside ND600A and forward packets outside of ND 600A; VNE 670A.1 is coupled withVNE 670H.1, and thus they communicate packets between their respectiveNDs; VNE 670A.2-670A.3 may optionally forward packets between themselveswithout forwarding them outside of the ND 600A; and VNE 670A.P mayoptionally be the first in a chain of VNEs that includes VNE 670A.Qfollowed by VNE 670A.R (this is sometimes referred to as dynamic servicechaining, where each of the VNEs in the series of VNEs provides adifferent service—e.g., one or more layer 4-7 network services). WhileFIG. 6C illustrates various exemplary relationships between the VNEs,alternative embodiments may support other relationships (e.g.,more/fewer VNEs, more/fewer dynamic service chains, multiple differentdynamic service chains with some common VNEs and some different VNEs).

The NDs of FIG. 6A, for example, may form part of the Internet or aprivate network; and other electronic devices (not shown; such as enduser devices including workstations, laptops, netbooks, tablets, palmtops, mobile phones, smartphones, phablets, multimedia phones, VoiceOver Internet Protocol (VOIP) phones, terminals, portable media players,GPS units, wearable devices, gaming systems, set-top boxes, Internetenabled household appliances) may be coupled to the network (directly orthrough other networks such as access networks) to communicate over thenetwork (e.g., the Internet or virtual private networks (VPNs) overlaidon (e.g., tunneled through) the Internet) with each other (directly orthrough servers) and/or access content and/or services. Such contentand/or services are typically provided by one or more servers (notshown) belonging to a service/content provider or one or more end userdevices (not shown) participating in a peer-to-peer (P2P) service, andmay include, for example, public webpages (e.g., free content, storefronts, search services), private webpages (e.g., username/passwordaccessed webpages providing email services), and/or corporate networksover VPNs. For instance, end user devices may be coupled (e.g., throughcustomer premise equipment coupled to an access network (wired orwirelessly)) to edge NDs, which are coupled (e.g., through one or morecore NDs) to other edge NDs, which are coupled to electronic devicesacting as servers. However, through compute and storage virtualization,one or more of the electronic devices operating as the NDs in FIG. 6Amay also host one or more such servers (e.g., in the case of the generalpurpose network device 604, one or more of the software instances 662A-Rmay operate as servers; the same would be true for the hybrid networkdevice 606; in the case of the special-purpose network device 602, oneor more such servers could also be run on a virtualization layerexecuted by the processor(s) 612); in which case the servers are said tobe co-located with the VNEs of that ND.

A virtual network is a logical abstraction of a physical network (suchas that in FIG. 6A) that provides network services (e.g., L2 and/or L3services). A virtual network can be implemented as an overlay network(sometimes referred to as a network virtualization overlay) thatprovides network services (e.g., layer 2 (L2, data link layer) and/orlayer 3 (L3, network layer) services) over an underlay network (e.g., anL3 network, such as an Internet Protocol (IP) network that uses tunnels(e.g., generic routing encapsulation (GRE), layer 2 tunneling protocol(L2TP), IPSec) to create the overlay network).

A network virtualization edge (NVE) sits at the edge of the underlaynetwork and participates in implementing the network virtualization; thenetwork-facing side of the NVE uses the underlay network to tunnelframes to and from other NVEs; the outward-facing side of the NVE sendsand receives data to and from systems outside the network. A virtualnetwork instance (VNI) is a specific instance of a virtual network on aNVE (e.g., a

NE/VNE on an ND, a part of a NE/VNE on a ND where that NE/VNE is dividedinto multiple VNEs through emulation); one or more VNIs can beinstantiated on an NVE (e.g., as different VNEs on an ND). A virtualaccess point (VAP) is a logical connection point on the NVE forconnecting external systems to a virtual network; a VAP can be physicalor virtual ports identified through logical interface identifiers (e.g.,a VLAN ID).

Examples of network services include: 1) an Ethernet LAN emulationservice (an Ethernet-based multipoint service similar to an InternetEngineering Task Force (IETF) Multiprotocol Label Switching (MPLS) orEthernet VPN (EVPN) service) in which external systems areinterconnected across the network by a LAN environment over the underlaynetwork (e.g., an NVE provides separate L2 VNIs (virtual switchinginstances) for different such virtual networks, and L3 (e.g., IP/MPLS)tunneling encapsulation across the underlay network); and 2) avirtualized IP forwarding service (similar to IETF IP VPN (e.g., BorderGateway Protocol (BGP)/MPLS IPVPN) from a service definitionperspective) in which external systems are interconnected across thenetwork by an L3 environment over the underlay network (e.g., an NVEprovides separate L3 VNIs (forwarding and routing instances) fordifferent such virtual networks, and L3 (e.g., IP/MPLS) tunnelingencapsulation across the underlay network)). Network services may alsoinclude quality of service capabilities (e.g., traffic classificationmarking, traffic conditioning and scheduling), security capabilities(e.g., filters to protect customer premises from network—originatedattacks, to avoid malformed route announcements), and managementcapabilities (e.g., full detection and processing).

FIG. 6D illustrates a network with a single network element on each ofthe NDs of FIG. 6A, and within this straight forward approach contrastsa traditional distributed approach (commonly used by traditionalrouters) with a centralized approach for maintaining reachability andforwarding information (also called network control), according to someembodiments of the invention. Specifically, FIG. 6D illustrates networkelements (NEs) 670A-H with the same connectivity as the NDs 600A-H ofFIG. 6A.

FIG. 6D illustrates that the distributed approach 672 distributesresponsibility for generating the reachability and forwardinginformation across the NEs 670A-H; in other words, the process ofneighbor discovery and topology discovery is distributed.

For example, where the special-purpose network device 602 is used, thecontrol communication and configuration module(s) 632A-R of the NDcontrol plane 624 typically include a reachability and forwardinginformation module to implement one or more routing protocols (e.g., anexterior gateway protocol such as Border Gateway Protocol (BGP),

Interior Gateway Protocol(s) (IGP) (e.g., Open Shortest Path First(OSPF), Intermediate System to Intermediate System (IS-IS), RoutingInformation Protocol (RIP), Label Distribution Protocol (LDP), ResourceReservation Protocol (RSVP) (including RSVP-Traffic Engineering (TE):Extensions to RSVP for LSP Tunnels and Generalized Multi-Protocol LabelSwitching (GMPLS) Signaling RSVP-TE)) that communicate with other

NEs to exchange routes, and then selects those routes based on one ormore routing metrics. Thus, the NEs 670A-H (e.g., the processor(s) 612executing the control communication and configuration module(s) 632A-R)perform their responsibility for participating in controlling how data(e.g., packets) is to be routed (e.g., the next hop for the data and theoutgoing physical NI for that data) by distributively determining thereachability within the network and calculating their respectiveforwarding information. Routes and adjacencies are stored in one or morerouting structures (e.g., Routing Information Base (RIB), LabelInformation Base (LIB), one or more adjacency structures) on the NDcontrol plane 624. The ND control plane 624 programs the ND forwardingplane 626 with information (e.g., adjacency and route information) basedon the routing structure(s). For example, the ND control plane 624programs the adjacency and route information into one or more forwardingtable(s) 634A-R (e.g., Forwarding Information Base (FIB), LabelForwarding Information Base (LFIB), and one or more adjacencystructures) on the ND forwarding plane 626. For layer 2 forwarding, theND can store one or more bridging tables that are used to forward databased on the layer 2 information in that data. While the above exampleuses the special-purpose network device 602, the same distributedapproach 672 can be implemented on the general-purpose network device604 and the hybrid network device 606.

FIG. 6D illustrates that a centralized approach 674 (also known assoftware defined networking (SDN)) that decouples the system that makesdecisions about where traffic is sent from the underlying systems thatforwards traffic to the selected destination. The illustratedcentralized approach 674 has the responsibility for the generation ofreachability and forwarding information in a centralized control plane676 (sometimes referred to as a SDN control module, controller, networkcontroller, OpenFlow controller, SDN controller, control plane node,network virtualization authority, or management control entity), andthus the process of neighbor discovery and topology discovery iscentralized. The centralized control plane 676 has a south boundinterface 682 with a data plane 680 (sometime referred to theinfrastructure layer, network forwarding plane, or forwarding plane(which should not be confused with a ND forwarding plane)) that includesthe NEs 670A-H (sometimes referred to as switches, forwarding elements,data plane elements, or nodes). The centralized control plane 676includes a network controller 678, which includes a centralizedreachability and forwarding information module 679 that determines thereachability within the network and distributes the forwardinginformation to the NEs 670A-H of the data plane 680 over the south boundinterface 682 (which may use the OpenFlow protocol). Thus, the networkintelligence is centralized in the centralized control plane 676executing on electronic devices that are typically separate from theNDs.

For example, where the special-purpose network device 602 is used in thedata plane 680, each of the control communication and configurationmodule(s) 632A-R of the ND control plane 624 typically include a controlagent that provides the VNE side of the south bound interface 682. Inthis case, the ND control plane 624 (the processor(s) 612 executing thecontrol communication and configuration module(s) 632A-R) performs itsresponsibility for participating in controlling how data (e.g., packets)is to be routed (e.g., the next hop for the data and the outgoingphysical NI for that data) through the control agent communicating withthe centralized control plane 676 to receive the forwarding information(and in some cases, the reachability information) from the centralizedreachability and forwarding information module 679 (it should beunderstood that in some embodiments of the invention, the controlcommunication and configuration module(s) 632A-R, in addition tocommunicating with the centralized control plane 676, may also play somerole in determining reachability and/or calculating forwardinginformation—albeit less so than in the case of a distributed approach;such embodiments are generally considered to fall under the centralizedapproach 674, but may also be considered a hybrid approach).

While the above example uses the special-purpose network device 602, thesame centralized approach 674 can be implemented with the generalpurpose network device 604 (e.g., each of the VNE 660A-R performs itsresponsibility for controlling how data (e.g., packets) is to be routed(e.g., the next hop for the data and the outgoing physical NI for thatdata) by communicating with the centralized control plane 676 to receivethe forwarding information (and in some cases, the reachabilityinformation) from the centralized reachability and forwardinginformation module 679; it should be understood that in some embodimentsof the invention, the VNEs 660A-R, in addition to communicating with thecentralized control plane 676, may also play some role in determiningreachability and/or calculating forwarding information—albeit less sothan in the case of a distributed approach) and the hybrid networkdevice 606. In fact, the use of SDN techniques can enhance the NFVtechniques typically used in the general-purpose network device 604 orhybrid network device 606 implementations as NFV is able to support SDNby providing an infrastructure upon which the SDN software can be run,and NFV and SDN both aim to make use of commodity server hardware andphysical switches.

FIG. 6D also shows that the centralized control plane 676 has a northbound interface 684 to an application layer 686, in which residesapplication(s) 688. The centralized control plane 676 has the ability toform virtual networks 692 (sometimes referred to as a logical forwardingplane, network services, or overlay networks (with the NEs 670A-H of thedata plane 680 being the underlay network)) for the application(s) 688.Thus, the centralized control plane 676 maintains a global view of allNDs and configured NEs/VNEs, and it maps the virtual networks to theunderlying NDs efficiently (including maintaining these mappings as thephysical network changes either through hardware (ND, link, or NDcomponent) failure, addition, or removal). The Applications 688 mayinclude AAA servers 683 and AAA clients 681 as described herein. The AAAclients may encompass AAA client applications and/or AAA protocolstacks. These embodiments further encompass Diameter implementations.

While FIG. 6D shows the distributed approach 672 separate from thecentralized approach 674, the effort of network control may bedistributed differently or the two combined in certain embodiments ofthe invention. For example: 1) embodiments may generally use thecentralized approach (SDN) 674, but have certain functions delegated tothe NEs (e.g., the distributed approach may be used to implement one ormore of fault monitoring, performance monitoring, protection switching,and primitives for neighbor and/or topology discovery); or 2)embodiments of the invention may perform neighbor discovery and topologydiscovery via both the centralized control plane and the distributedprotocols, and the results compared to raise exceptions where they donot agree. Such embodiments are generally considered to fall under thecentralized approach 674, but may also be considered a hybrid approach.

While FIG. 6D illustrates the simple case where each of the NDs 600A-Himplements a single NE 670A-H, it should be understood that the networkcontrol approaches described with reference to FIG. 6D also work fornetworks where one or more of the NDs 600A-H implement multiple VNEs(e.g., VNEs 630A-R, VNEs 660A-R, those in the hybrid network device606). Alternatively or in addition, the network controller 678 may alsoemulate the implementation of multiple VNEs in a single ND.Specifically, instead of (or in addition to) implementing multiple VNEsin a single ND, the network controller 678 may present theimplementation of a VNE/NE in a single ND as multiple VNEs in thevirtual networks 692 (all in the same one of the virtual network(s) 692,each in different ones of the virtual network(s) 692, or somecombination). For example, the network controller 678 may cause an ND toimplement a single VNE (a NE) in the underlay network, and thenlogically divide up the resources of that NE within the centralizedcontrol plane 676 to present different VNEs in the virtual network(s)692 (where these different VNEs in the overlay networks are sharing theresources of the single VNE/NE implementation on the ND in the underlaynetwork).

On the other hand, FIGS. 6E and 6F respectively illustrate exemplaryabstractions of NEs and VNEs that the network controller 678 may presentas part of different ones of the virtual networks 692. FIG. 6Eillustrates the simple case of where each of the NDs 600A-H implements asingle NE 670A-H (see FIG. 6D), but the centralized control plane 676has abstracted multiple of the NEs in different NDs (the NEs 670A-C andG-H) into (to represent) a single NE 6701 in one of the virtualnetwork(s) 692 of FIG. 6D, according to some embodiments of theinvention. FIG. 6E shows that in this virtual network, the NE 6701 iscoupled to NE 670D and 670F, which are both still coupled to NE 670E.

FIG. 6F illustrates a case where multiple VNEs (VNE 670A.1 and VNE670H.1) are implemented on different NDs (ND 600A and ND 600H) and arecoupled to each other, and where the centralized control plane 676 hasabstracted these multiple VNEs such that they appear as a single VNE670T within one of the virtual networks 692 of FIG. 6D, according tosome embodiments of the invention. Thus, the abstraction of a NE or VNEcan span multiple NDs.

While some embodiments of the invention implement the centralizedcontrol plane 676 as a single entity (e.g., a single instance ofsoftware running on a single electronic device), alternative embodimentsmay spread the functionality across multiple entities for redundancyand/or scalability purposes (e.g., multiple instances of softwarerunning on different electronic devices).

Similar to the network device implementations, the electronic device(s)running the centralized control plane 676, and thus the networkcontroller 678 including the centralized reachability and forwardinginformation module 679, may be implemented a variety of ways (e.g., aspecial purpose device, a general-purpose (e.g., COTS) device, or hybriddevice). These electronic device(s) would similarly includeprocessor(s), a set or one or more physical NIs, and a non-transitorymachine-readable storage medium having stored thereon the centralizedcontrol plane software. For instance, FIG. 7 illustrates, ageneral-purpose control plane device 704 including hardware 740comprising a set of one or more processor(s) 742 (which are often COTSprocessors) and physical NIs 746, as well as non-transitorymachine-readable storage media 748 having stored therein centralizedcontrol plane (CCP) software 750.

In embodiments that use compute virtualization, the processor(s) 742typically execute software to instantiate a virtualization layer 754(e.g., in one embodiment the virtualization layer 754 represents thekernel of an operating system (or a shim executing on a base operatingsystem) that allows for the creation of multiple instances 762A-R calledsoftware containers (representing separate user spaces and also calledvirtualization engines, virtual private servers, or jails) that may eachbe used to execute a set of one or more applications; in anotherembodiment the virtualization layer 754 represents a hypervisor(sometimes referred to as a virtual machine monitor (VMM)) or ahypervisor executing on top of a host operating system, and anapplication is run on top of a guest operating system within an instance762A-R called a virtual machine (which in some cases may be considered atightly isolated form of software container) that is run by thehypervisor ; in another embodiment, an application is implemented as aunikernel, which can be generated by compiling directly with anapplication only a limited set of libraries (e.g., from a libraryoperating system (LibOS) including drivers/libraries of OS services)that, provide the particular OS services needed by the application, andthe unikernel can run directly on hardware 740, directly on a hypervisorrepresented by virtualization layer 754 (in which case the unikernel issometimes described as running within a LibOS virtual machine), or in asoftware container represented by one of instances 762A-R). Again, inembodiments where compute virtualization is used, during operation aninstance of the CCP software 750 (illustrated as CCP instance 776A) isexecuted (e.g., within the instance 762A) on the virtualization layer754. In embodiments where compute virtualization is not used, the CCPinstance 776A is executed, as a unikernel or on top of a host operatingsystem, on the “bare metal” general purpose control plane device 704.The instantiation of the CCP instance 776A, as well as thevirtualization layer 754 and instances 762A-R if implemented, arecollectively referred to as software instance(s) 752.

In some embodiments, the CCP instance 776A includes a network controllerinstance 778. The network controller instance 778 includes a centralizedreachability and forwarding information module instance 779 (which is amiddleware layer providing the context of the network controller 678 tothe operating system and communicating with the various NEs), and an CCPapplication layer 780 (sometimes referred to as an application layer)over the middleware layer (providing the intelligence required forvarious network operations such as protocols, network situationalawareness, and user—interfaces). At a more abstract level, this CCPapplication layer 780 within the centralized control plane 676 workswith virtual network view(s) (logical view(s) of the network) and themiddleware layer provides the conversion from the virtual networks tothe physical view. The Application layer 780 may support AAA servers 783and AAA clients 681 as described herein. The AAA clients may encompassAAA client applications and/or AAA protocol stacks. These embodimentsfurther encompass Diameter implementations.

The centralized control plane 676 transmits relevant messages to thedata plane 680 based on CCP application layer 780 calculations andmiddleware layer mapping for each flow. A flow may be defined as a setof packets whose headers match a given pattern of bits; in this sense,traditional IP forwarding is also flow-based forwarding where the flowsare defined by the destination IP address for example; however, in otherimplementations, the given pattern of bits used for a flow definitionmay include more fields (e.g., 10 or more) in the packet headers.Different NDs/NEs/VNEs of the data plane 680 may receive differentmessages, and thus different forwarding information. The data plane 680processes these messages and programs the appropriate flow informationand corresponding actions in the forwarding tables (sometime referred toas flow tables) of the appropriate NE/VNEs, and then the NEs/VNEs mapincoming packets to flows represented in the forwarding tables andforward packets based on the matches in the forwarding tables.

Standards such as OpenFlow define the protocols used for the messages,as well as a model for processing the packets. The model for processingpackets includes header parsing, packet classification, and makingforwarding decisions. Header parsing describes how to interpret a packetbased upon a well-known set of protocols. Some protocol fields are usedto build a match structure (or key) that will be used in packetclassification (e.g., a first key field could be a source media accesscontrol (MAC) address, and a second key field could be a destination MACaddress).

Packet classification involves executing a lookup in memory to classifythe packet by determining which entry (also referred to as a forwardingtable entry or flow entry) in the forwarding tables best matches thepacket based upon the match structure, or key, of the forwarding tableentries. It is possible that many flows represented in the forwardingtable entries can correspond/match to a packet; in this case the systemis typically configured to determine one forwarding table entry from themany according to a defined scheme (e.g., selecting a first forwardingtable entry that is matched). Forwarding table entries include both aspecific set of match criteria (a set of values or wildcards, or anindication of what portions of a packet should be compared to aparticular value/values/wildcards, as defined by the matchingcapabilities—for specific fields in the packet header, or for some otherpacket content), and a set of one or more actions for the data plane totake on receiving a matching packet. For example, an action may be topush a header onto the packet, for the packet using a particular port,flood the packet, or simply drop the packet. Thus, a forwarding tableentry for IPv4/IPv6 packets with a particular transmission controlprotocol (TCP) destination port could contain an action specifying thatthese packets should be dropped.

Making forwarding decisions and performing actions occurs, based uponthe forwarding table entry identified during packet classification, byexecuting the set of actions identified in the matched forwarding tableentry on the packet.

However, when an unknown packet (for example, a “missed packet” or a“match-miss” as used in OpenFlow parlance) arrives at the data plane680, the packet (or a subset of the packet header and content) istypically forwarded to the centralized control plane 676. Thecentralized control plane 676 will then program forwarding table entriesinto the data plane 680 to accommodate packets belonging to the flow ofthe unknown packet. Once a specific forwarding table entry has beenprogrammed into the data plane 680 by the centralized control plane 676,the next packet with matching credentials will match that forwardingtable entry and take the set of actions associated with that matchedentry.

A network interface (NI) may be physical or virtual; and in the contextof IP, an interface address is an IP address assigned to a NI, be it aphysical NI or virtual NI. A virtual NI may be associated with aphysical NI, with another virtual interface, or stand on its own (e.g.,a loopback interface, a point-to-point protocol interface). A NI(physical or virtual) may be numbered (a NI with an IP address) orunnumbered (a NI without an IP address). A loopback interface (and itsloopback address) is a specific type of virtual NI (and IP address) of aNE/VNE (physical or virtual) often used for management purposes; wheresuch an IP address is referred to as the nodal loopback address. The IPaddress(es) assigned to the NI(s) of a ND are referred to as IPaddresses of that ND; at a more granular level, the IP address(es)assigned to NI(s) assigned to a NE/VNE implemented on a ND can bereferred to as IP addresses of that NE/VNE.

While the invention has been described in terms of several embodiments,those skilled in the art will recognize that the invention is notlimited to the embodiments described, can be practiced with modificationand alteration within the spirit and scope of the appended claims. Thedescription is thus to be regarded as illustrative instead of limiting.

1. A method for migrating a subscriber session from a firstauthentication, authorization, and accounting (AAA) authenticationserver to a second AAA authentication server, where the first AAAauthentication server is stateful, the method comprising: receiving anauthenticate session request from a client application; sending theauthenticate session request to the first AAA authentication server;detecting connectivity failure with the first AAA authentication server;and sending a reauthentication required message to the clientapplication.
 2. The method of claim 1, further comprising: generating,by the AAA client, the reauthentication required message to be sent tothe client application.
 3. The method of claim 1, further comprising:selecting the first AAA authentication server from a set of availableAAA authentication servers.
 4. The method of claim 1, furthercomprising: selecting the second AAA authentication server from a set ofavailable AAA authentication servers.
 5. The method of claim 1, whereinan AAA protocol utilized by the first AAA authentication server, secondAAA authentication server, AAA protocol stack and AAA client applicationis Diameter.
 6. A network device configured to execute a plurality ofvirtual machines, the virtual machines configured to support networkfunction virtualization (NFV), the plurality of virtual machines tosupport a method for migrating a subscriber session from a firstauthentication, authorization, and accounting (AAA) authenticationserver to a second AAA authentication server, where the first AAAauthentication server is stateful, the network device comprising: anon-transitory computer readable medium having stored therein a AAAclient; and a processor coupled to the non-transitory computer readablemedium configured to execute a virtual machine from the plurality ofvirtual machine, the virtual machine to execute the AAA client, the AAAclient configured to receive an authenticate session request from aclient application, to send the authenticate session request to thefirst AAA authentication server, to detect connectivity failure with thefirst AAA authentication server, and to send a reauthentication requiredmessage to the client application.
 7. The network device of claim 6,wherein the AAA client is further to generate the reauthenticationrequired message to be sent to the client application.
 8. The networkdevice of claim 6, wherein the AAA client is further to select the firstAAA authentication server from a set of available AAA authenticationservers.
 9. The network device of claim 6, wherein the AAA client isfurther to select the second AAA authentication server from a set ofavailable AAA authentication servers.
 10. The network device of claim 6,wherein an AAA protocol utilized by the first AAA authentication server,second AAA authentication server, AAA protocol stack and AAA clientapplication is Diameter.
 11. A computing device configured to execute amethod for migrating a subscriber session from a first authentication,authorization, and accounting (AAA) authentication server to a secondAAA authentication server, where the first AAA authentication server isstateful, the computing device comprising: a non-transitory computerreadable medium having stored therein a AAA client; and a processorcoupled to the non-transitory computer readable medium configured toexecute the AAA client, the AAA client configured to receive anauthenticate session request from a client application, to send theauthenticate session request to the first AAA authentication server, todetect connectivity failure with the first AAA authentication server,and to send a reauthentication required message to the clientapplication.
 12. The computing device of claim 11, wherein the AAAclient is further to generate the reauthentication required message tobe sent to the client application.
 13. The computing device of claim 11,wherein the AAA client is further to select the first AAA authenticationserver from a set of available AAA authentication servers.
 14. Thecomputing device of claim 11, wherein the AAA client is further toselect the second AAA authentication server from a set of available AAAauthentication servers.
 15. The computing device of claim 11, wherein anAAA protocol utilized by the first AAA accounting server, second AAAaccounting server, AAA protocol stack and AAA client application isDiameter.
 16. A control plane device in a network including a pluralityof data plane devices, the control plane device in communication withthe plurality of data plane devices and configured to implement a methodfor migrating a subscriber session from a first authentication,authorization, and accounting (AAA) authentication server to a secondAAA authentication server, where the first AAA authentication server isstateful, the control plane device comprising: a non-transitory computerreadable medium having stored therein a AAA client; and a processorcoupled to the non-transitory computer readable medium configured toexecute the AAA client, the AAA client configured to receive anauthenticate session request from a client application, to send theauthenticate session request to the first AAA authentication server, todetect connectivity failure with the first AAA authentication server,and to send a reauthentication required message to the clientapplication.
 17. The control plane device of claim 16, wherein the AAAclient is further to generate the reauthentication required message tobe sent to the client application.
 18. The control plane device of claim16, wherein the AAA client is further to select the first AAAauthentication server from a set of available AAA authenticationservers.
 19. The control plane device of claim 16, wherein the AAAclient is further to select the second AAA authentication server from aset of available AAA authentication servers.
 20. The control planedevice of claim 16, wherein an AAA protocol utilized by the first AAAaccounting server, second AAA accounting server, AAA protocol stack andAAA client application is Diameter.